A biosensor may be denoted as a device to be used for the detection of an analyte that combines a biological component with a physicochemical or physical detector component.
For instance, a biosensor may be based on the phenomenon that capture particles immobilized on a surface of a biosensor, may selectively attach with target particles in a fluidic sample, for instance when an antibody-binding fragment of an antibody or the sequence of a DNA single strand as a capture particle fits to a corresponding sequence or structure of a target particle. When such attachment or sensor events occur at the sensor surface, this may change the electrical properties of the surface, which can be detected as the sensor event.
G. Barillaro, A. Diligenti, L. M. Strambini, “p+-n diodes with a lateral porous layer as gas sensors”, Physica Status Solidi (a), Volume 204, Issue 5, pp. 1399-1403 discloses an integrated p+-n diode, diffused on a crystalline substrate and provided with a thin adsorbing porous layer as gas sensor. The sensor can be integrated by using an industrial CMOS process due to the fact that the porous film formation is the last process step. The sensitivity to isopropanol vapors has been investigated by measuring both the forward and reverse current of the diode as a function of the vapor concentration. The current variations, up to two orders of magnitude, could be explained by assuming that the adsorption of particles in the porous layer and their interaction with localized states modify the band structure of the crystalline diode at the interface with the porous silicon, and in turn its current. Another sensor feature is that the value of the reverse current variation, induced by isopropanol vapors, depends on the voltage, so that the sensitivity can be settled by simply changing the reverse voltage itself.